Field of the Invention
The present invention relates to products made or derived from tobacco, or that otherwise incorporate tobacco, and are intended for human consumption. Aspects of the present disclosure are directed to devices for slitting sheet material and, more particularly, to an apparatus and an associated method for cutting a sheet material for use in the manufacture of tobacco products such as cigarettes.
Description of Related Art
Smoking articles, such as cigarettes, typically have a substantially cylindrical structure and include a charge, roll or column of smokable material such as shredded tobacco surrounded by a paper wrapper, thereby forming a tobacco rod.
The roll or column of tobacco used to fill the tobacco rod used in the manufacture of cigarettes may be cut from reconstituted tobacco sheet (such as, for example, R.J. Reynolds Tobacco Company so-called G-7 reconstituted tobacco sheet). Representative methods for making certain types of reconstituted tobacco sheet using papermaking-type processes are set forth, for example, in U.S. Pat. No. 3,847,164 to Mattina; U.S. Pat. No. 4,131,117 to Kite et at; U.S. Pat. No. 4,182,349 to Selke; U.S. Pat. No. 4,308,877 to Mattina; U.S. Pat. No. 4,341,228 to Keritsis; U.S. Pat. No. 4,421,126 to Gellatly; U.S. Pat. No. 4,706,692 to Gellatly; U.S. Pat. No. 4,941,484 to Clapp et al.; U.S. Pat. No. 4,962,774 to Thomasson et al.; U.S. Pat. No. 4,987,906 to Young et at; U.S. Pat. No. 5,056,537 to Brown et al.; U.S. Pat. No. 5,143,097 to Sohn et al.; U.S. Pat. No. 5,322,076 to Brinkley et al.; U.S. Pat. No. 5,325,877 to Young et al.; U.S. Pat. No. 5,377,698 to Litzinger; U.S. Pat. No. 5,445,169 to Brinkley et al.; U.S. Pat. No. 5,501,237 to Young et al.; and U.S. Pat. No. 5,533,530 to Young et al.; which are incorporated herein by reference.
In one representative process, the tobacco sheet, once formed from the tobacco pulp material, is then dried to about 12% moisture and has a temperature slightly greater than ambient before being directed to a downstream slitter device for slitting the sheet into ribbons of various widths such as, for example, on the order of about 1-3 inches wide. In some instances, the tobacco sheet, such as, for example, a G-7 reconstituted tobacco sheet, is about 85 inches wide (with standard thickness and basis weight of a reconstituted tobacco sheet) and is directed to travel at about 400 feet/minute in a machine direction to the slitter device.
Some slitter devices used in the production of tobacco products may have one or more rotating shafts, extending non-parallel to the machine direction, with blades or knives attached thereto at lateral intervals corresponding to the desired width of the ribbons that are to be cut from the sheet material, such as that disclosed by U.S. Patent Application Publication No. 2005/0217447 to Hollandsworth et al., which is hereby incorporated herein by reference. In multi-shaft slitters, first and second shafts are generally mounted in close proximity and have substantially parallel rotational axes. In these devices, the blades attached to the first shaft are configured to interact with the second shaft and/or complementary blades attached to the second shaft. This configuration provides a precise shearing cut of the sheet material as it is directed through the slitter between the parallel rotating shafts. A two-shaft, complementary-blade arrangement has been described, for example, in U.S. Pat. No. 4,449,540 to Marshall et al., wherein a slitter-type machine is disclosed for cutting baled tobacco. According to the '540 patent, complementary circular blades or discs on parallel shafts provide a shearing action to cut baled tobacco into sections of a specified width.
In addition, U.S. Pat. No. 4,566,470 to Bradman discloses the general use of closely-spaced counter-rotating discs to shred fibrous tobacco stem material to produce tobacco material suitable for use in cigarette production. Additionally, U.S. Pat. No. 5,445,054 to Pryor generally discloses the use of a tobacco sheet cutting apparatus having a fixed ledger blade, and a rotatable cutter blade co-acting with the ledger blade, to simultaneously cut a tobacco sheet into slit pieces used for cut filler in a cigarette making process. Yet another system for slitting reconstituted tobacco sheet material is set forth in U.S. Pat. No. 5,025,814 to Raker.
In any instance, after repeated contact with the sheet material and the various components and/or other material therein, such as plant stem material, and other relatively harder particles, including soil and mineral components, the blades may begin to wear. Blade wear may occur in a non-uniform manner such that, in some instances, certain blades may exhibit more wear than other blades. This wear can result in deterioration of slitter performance, since the complementary blades become “dulled” and can no longer provide the necessary “sharp” cutting action to cleanly cut the sheet material.
Some tobacco cutting machines disclosed in the prior art, such as in U.S. Pat. No. 3,320,991 to Molins, provide a self-adjusting sharpening mechanism built into the machine for periodic re-sharpening of a collection of cutting blades attached to a single cutting drum. Another single shaft tobacco cutting machine is disclosed in U.S. Pat. No. 3,322,175 to Ward, wherein a clamp for providing a consistent clamping force on cutting knives affixed to a single rotating drum is disclosed.
In some previous slitter machines, realignment of complementary slitter blades into an appropriate cutting relation may require dismantling of all or part of the slitter machine. Such a process includes, for example, removal of the ledger bar section and realignment thereof in order to bring the blades on the ledger bar section into the appropriate cutting/shearing positions relative to complementary blades on the rotatable cutter blade. Such a dismantling and realignment process may be disadvantageous due to the labor-intensive nature of the process and resulting machine down time. In some instances, less than optimal alignment of the blades upon reassembly may undesirably necessitate one or more iterations of the realignment process.
Thus, there exists a need for a cutting apparatus capable of compensating for blade wear without the associated disadvantages of exemplary prior art slitter devices.